The mission could not have been set on a more challenging landscape, at a more inopportune time.

Many in Louisiana’s coastal scientific community believe DeLuca’s description is right on the mark, capturing the undertaking’s daunting uncertainties.

DeLuca, an expert on the many threats facing the coast, said: “It will take a moon-shot type of investment in the science.”

As Brig. Gen Duke DeLuca wrapped up his 32-year career with the U.S. Army Corps of Engineers in August, he contemplated the key to Louisiana’s massive, 50-year, $50 billion effort to prevent the southeastern portion of the state from being swallowed by the Gulf of Mexico.

This story is second in a two-part series on Louisiana’s rapidly disappearing coastline. Read part one .

and money it doesn’t have. What could go wrong?

Losing Ground Louisiana’s Moon Shot The state hopes to save its rapidly disappearing coastline with a 50-year, $50 billion plan based on science that’s never been tested and money it doesn’t have. What could go wrong?

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2014 A Canal spoil levees These straight lines show where mud was dumped as canals were dredged for oil and gas drilling. The canals led to such dramatic wetlands losses that in some areas just the spoil levees remain, surrounded by open water in what was once thick marsh. B Containment berms Before the project began, mud berms were built around the area. They prevented the mixture of sediment and water from washing away. C Bayou Hermitage Bayous connected to the Mississippi once helped build land far from the banks of the river. That process ended when levees cut the river off from the bayous. The marshes nearby remain because they live on the natural levee built during spring floods. Lake Hermitage: Pumping new life into the wetlands The state can restore some areas quickly, but it’s a short-term fix Slurry pipelines, one way to rebuild Louisiana’s wetlands, are proven to work. Sediment is dredged from the bottom of the river and offshore, mixed with water and pumped to sunken basins or eroded beaches — sometimes many miles away. The state has used slurry pipelines to rebuild two areas of wetlands near the river and several beachfronts along the Gulf. This technique can quickly fill a bay with land 2 feet high. In about two years, the Lake Hermitage Marsh Creation Project, on the west side of the river about 30 miles south of New Orleans, filled in about 700 acres of wetlands that had turned to open water. Some in the fishing industry prefer pipelines over diversions because diversions would dramatically reduce water salinity, which probably will push their targeted species away from traditional fishing grounds. Although they’re fast and cheap in the short-term, slurry pipelines are a temporary fix. Over time, the new land will sink, and in about 30 years the state will have to repeat the process.

Source: USGS, Digital Globe

Another targets the Biloxi Marsh, an isolated section of wetlands on the state's far eastern edge that protects greater New Orleans and provides a key fisheries habitat. This project would create and restore 33,000 acres of wetlands at a cost of $3 billion. Slurry pipelines produce results quickly. They can fill 500 acres of open water with land 2 feet high in six months. But they have two serious drawbacks. The new land will sink, too, so these areas will have to be rebuilt in 30 to 40 years. And the farther that the sand and mud must be pumped, the more it costs. Imitating nature The second method of rebuilding wetlands, controlled sediment diversions, doesn't have those problems. But one has never been built. The idea is to move some of the freshwater and sediment in the Mississippi River to where it's needed most. When the river is high, specially designed gates would be opened in the river levee, allowing freshwater and sediment to wash over nearby areas. These diversions would build land over decades, not months. Theoretically, they would work as long as the river flows. "The one advantage this delta has over the many others that are in trouble is that we still have a river delivering the material to help get us out of trouble," said Denise Reed, chief scientist at the Water Institute of the Gulf. "As long as that river is bringing the sediments to us, we have a chance." Sediment diversions cost hundreds of millions each compared to tens of millions for slurry pipelines, but some studies have shown they're worth it in the long run. Five sediment diversions are planned to rebuild vast expanses of wetlands in the roughly 60 miles between metro New Orleans and Buras, the last big bend in the river before it meets the Gulf. The restoration plan calls for spending $4 billion on diversions to build and preserve 300 square miles of land and $20 billion on slurry pipelines that will result in 200 square miles.

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2014 Although the sediment diversion was cut in 2003, little land built up over the next several years. Beginning in 2009, three islands were built to slow the water as it flowed into the bay. Bit by bit, land started to rise above the water. Land is now building steadily in West Bay. The West Bay diversion project demonstrated that the river, once reconnected to its delta, can rebuild lost land Sediment diversions — dam-like structures built into the levee — are one of two key methods to rebuild wetlands that have sunk below the water. When the river is high, gates will be opened, allowing sediment-laden water to run across the deltas. Diversions have a higher initial cost than slurry pipelines, and they begin building new wetlands more slowly, but engineers consider them a permanent repair because they can supply sediment as long as the river flows. The state points to this project near the mouth of the Mississippi River as proof this strategy can work. In 2003, the U.S. Army Corps of Engineers opened a 200-yard gap on the west bank of the river south of Venice, leading into West Bay. That area was once filled with cypress swamps; now it’s open water. For six years, little new land appeared. But beginning in 2009, on the advice of local rancher Earl Armstrong, the corps built three small islands to slow down the water as it entered the bay. Silt began to drift to the bottom of the bay rather than get swept into deeper water. By the next year, new delta lands began to emerge. Today, more than 1,000 new acres, filled with plants, have spread across the bay. Land continues to rise above the water. However, the West Bay diversion may be a lost cause. The state doesn’t plan to restore this area because it’s sinking about 5 feet a century and diversions upriver, meant to protect New Orleans and other communities, will further reduce the sediment it needs to stay above water.

Source: USGS, ProPublica/The Lens/Public Lab

What we give up Regardless of the method, the state doesn't believe there's enough sediment in the river to save everything. Wetlands along the last 40 miles to the Gulf, including those near the mouth of the river referred to as the Bird's Foot Delta, are not in the restoration plan. These wetlands, already sinking 5 feet a century and far from any large community, will get even less sediment when diversions are opened upriver. "It is a matter of physics and geology," said David Muth, director of the Gulf Restoration Program for the National Wildlife Federation. The current plan, he said, "merely proposes not wasting large sums of precious restoration dollars in a place with no future." Even some people who are fighting to extend the life of the Bird's Foot, like rancher Earl Armstrong, acknowledge that reality. Born and raised on the river at Pilottown, nine miles from the nearest road, he now uses airboats to keep an eye on his cattle on the shrinking spits of land. Armstrong advised the Corps of Engineers a few years ago on the West Bay diversion, the first major effort to build land by cutting a hole in the riverbank south of Venice. His advice was so important, one of the emerging islands is now named after him. But he fears he is fighting a losing battle. "We probably waited too long to get started," he said. "I would love for my grandchildren to know what I knew on this river, but it won't be here. It's going too quick." Mastering a complex game Although diversions have long been the centerpiece of discussions to restore the coast, the state hasn't committed to build even one. A decision isn't expected until fall 2015 because the science and engineering is more complicated than the slogans. "My concern is that a lot of people think if we just turn the river loose, it will just fill in all those holes we've created in the delta," said Roberts. "Well, certainly it's not as simple as punching holes in the levees." Every diversion project is a move in an ongoing chess match with nature. Each one faces different sets of variables and constraints, and engineers are struggling to anticipate the consequences of each step they take. "Everything you do at one point on the river — anything you take out or put in — will have an effect on the rest of the river," said Alex McCorquodale, a University of New Orleans researcher working on a study to determine how much sediment is in the lower Mississippi. These challenges came into focus as the state began planning the Mid-Barataria Diversion at Myrtle Grove, a $1.1 billion project about 30 miles south of New Orleans. With $275 million in initial funding already in place, it would be the first diversion to be built. The diversion would be located at the northern end of the Barataria Basin, an estuary important to seafood production and to protecting the New Orleans area from storm surge. If nothing is done, this area is predicted to lose 234 square miles of coastline over 50 years. Twenty-two square miles of that could be saved over 20 years — if the diversion is fed with enough of the right kind of sediment, flowing over the right wetlands infrastructure, according to computer models. The state is still trying to answer the many questions that could make or break those plans. The first one: Is there enough sediment in the river to get the job done? Sections of piping used to fill in sunken areas of wetlands rest on new land near the site of the former Manila Village settlement south of New Orleans. (Edmund D. Fountain for ProPublica/The Lens) Researchers know the river carries only half the sediment it once did. Much is trapped behind dams on Midwestern tributaries, while modern farming methods have reduced soil runoff. They are only now in the final stages of a study to determine if enough reaches the bottom section of the river and if it's the right type of sediment to build land. The diversion will be able to deliver 250,000 cubic feet per second, or as much as Niagara Falls at its peak. But computer models have shown that running the diversion at that capacity could increase the risk of flooding nearby communities such as Lafitte. That, in turn, could force the state to raise the levees around Lafitte. If it costs too much to do that, the state will have to reduce how much water goes through the diversion. Less water will build less land. High water flows also could hurt fishing. Louisiana's commercial and sports fishermen have led the Gulf in catches in a system that has gradually become more salty due to erosion. Now some are concerned that their target species — such as shrimp, oysters and speckled trout — will be displaced when fresh water pours in. The Save Louisiana Coalition, a fishing industry group, wants the state to scrub diversions from its restoration plan and focus only on slurry pipelines. Research is underway to determine how much fishing would be disrupted by operating diversions at different volumes. Planners need to figure out if the amount of land created, and the benefits to storm protection, would offset the economic losses that some fishers say will result. The vagaries of the river's flow and geology means you can't build a diversion just anywhere. It must be on a stretch where the right kind of sands and sediment can be captured, and the open water nearby isn't too deep and wide to be filled in. There must be enough of the original delta framework to aid in building land. And the wetlands must be built in places where they protect communities from hurricane surges. Big Projects Project Cost Apollo Program $146.6B Louisiana Coastal Master Plan $50B Manhattan Project $32.6B Total FEMA Assistance to Louisiana after Hurricanes Katrina and Rita $21.7B Hoover Dam Appropriation $2.58B Costs are in 2014 dollars. Apollo Program is money spent between 1959 and 1975, inflation adjusted from 1966. FEMA assistance was spent between 2005 and 2013, inflation adjusted from 2008. Sources: NASA, FEMA, Louisiana Coastal Protection and Restoration Authority, Brookings Institution, U.S. Bureau of Reclamation Rivers typically build deltas slowly in what looks like a random pattern of constantly shifting channels, islands and sandbars. To the casual observer "it may look like chaos, to a geologist like me it's poetry," said Kemp of LSU. Recreating that poetry is the key to building land. "In some of these areas, we did so much damage with the canal dredging, there is really nothing left of that original land-building system — the old channels, and ridges — that the river used to follow," Kemp said. "We're starting with basically a blank slate." If scientists manage to navigate all of these potential pitfalls, they'll still need to make sure the shipping channel to the nation's largest port remains open. That will limit how much water can be sent to resuscitate dying wetlands. Enough water must remain in the river to allow massive ships to pass. A recent study concluded that opening just one of the planned diversions at a maximum flow of 250,000 cubic feet per second would dramatically reduce the amount of water left in the lower river. If all five diversions were open at the same time, would they take so much water that shipping would be jeopardized? No one knows. "Shipping is just one of the constraints we have to consider when we do our modeling," said Graham, the head of the state coastal agency. Considering how much remains unknown, a few scientists ask why Louisiana has staked so much on diversions. They worry the state could waste its last chance for the coast on a technique they believe poses its own habitat threats and exists only on computer models. Gene Turner, a distinguished LSU coastal researcher, points to studies that show high levels of nutrients from fertilizer upstream can cause wetlands loss by damaging plants in areas with high organic soils. He is concerned that the state doesn't have a backup plan if its computer models are wrong. "Every building code requires a fire exit, and right now this plan doesn't have one," he said. "Saying, 'This is going to work' isn't a backup plan, not when you're doing something that has never been done before, except on computers." Turner has the minority view in the coastal scientific community. Nonetheless, the state coastal agency has asked the Water Institute of the Gulf to gather a panel of outside coastal experts to look into those questions. "We've got one chance to get this right," Turner said, "so we shouldn't be ignoring any of these warning signs."

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2014 Nature, with help Bay Denesse shows that by using the natural flow of river water, wetlands can be restored at a relative bargain. Most of the projects to rebuild Louisiana’s wetlands will cost tens of millions of dollars because manmade levees stand between the river and the dying delta. The price of restoration drops dramatically downriver, where there are no levees along the riverbank. Here, the river needs only a little help to reach its ailing wetlands. The wetlands around Bay Denesse, about 50 miles southeast of New Orleans, flood each spring. No new land was created, however, because the floods were too short and the water flowed too quickly to allow sediment to settle to the bottom. That began to change in 1973 when a record flood punched through the riverbank, creating a crevasse — an opening through which water could flow more often. Slowly, new wetlands began to emerge. In 2006, the state and federal government decided to build on that progress. They cut six crevasses into the riverbank. To slow down the water, they built 98 terraces — berms of soil about 200 feet long and 10 feet high. It’s working. Today, satellite images show the bottom of the bay filling with sediment — not just around the terraces but in adjoining bays. More than 300 acres have been created; more is expected as long as the river flows. The cost: $3 million — a bargain compared to most of the other projects in the restoration plan.

Source: USGS, Digital Globe